July 31st, 2023
Well the last day of July and probably many of you will be wishing an end to the seemingly constant run of wind and rain that has characterised this month.
A month ago, I was writing the exact opposite, as the 5 week hot and dry spell that characterised mid-May to the end of June had put everyone on their back foot and casting nervous glances to their water usage and reservoir levels.
That was our hottest ever June, what will July be ?
Our coolest, wettest maybe ? (Can't wait for The Met Office's verdict sometime this week when their super computer churns out the stats)
June and July 2023 characterise the 'flip a coin' nature of our weather now as the jet stream pushes us into an un-forecasted trough or peak pattern and we either get excessive heat or excessive rain. I saw yesterday, some areas have received over 300% of their normal July rainfall.
It is no wonder that the areas we need to look at are drainage, irrigation and of course water usage.
Not bad news for everyone
Sitting in my favourite coffee shop yesterday in Oakham (Strays), prior to going out for a walk around Rutland Water's Hambleton peninsular, I was thinking about whether this run of weather was good or bad news for insects. I'm seeing lots of butterflies, plenty of midges, but also concerningly, quite a lot of dead Bumblebees. The Swifts, Martins and Swallows seem to be enjoying it though.
My thought process was broken by the sight of a large insect buzzing around the hanging baskets outside. It struck a mental chord, hang on, I have seen this fellow before. It was a Hummingbird Hawk Moth, a really beautiful creature that flies and feeds like a Hummingbird, but it is a moth, not a bird.
Below is a pic I took in The Cevenne, France some years ago of the same insect.
Here, it is a summer migrant that is becoming a more regular visitor because no doubt, of climate change in our country. Winners and losers I guess.....
A false autumn ?
Walking along yesterday, the verges were populated with flowers and berries that I would normally see in the autumn. Blackberries are close to ready, mushrooms and fungi abound as the run of wet, humid weather has kicked them into action.
But we are only just going into August. What happens if it is a scorcher, if the jet stream flips the other way and we pick up a heat plume ? What happens then to nature ?
So that leads me into the weather for this week and next....
General Weather Situation
Well no way to dress this week's weather up nicely, we are in for a very wet week,I am afraid. A week that gets cooler as well as windier as the trailing edge of a low pressure system pulls down northerly winds from mid-week. (see below)
As you can see from the GFS projection for mid-week, this week, courtesy of tropicaltidbits.com, we have a continuation of our low pressure-dominated, trough pattern in the jet stream and a northerly airflow.
So Monday sees rain across Ireland, Scotland, The North West and the north of England from the off and it is here that it will stay most of the day, so for South Wales and the southern half of the U.K, not a bad day today, a bit dull, but when you consider what's coming later in the week. Not completely dry though because we will see showers morphing into longer spells of rain cross northern England, The Midlands into East Anglia during the day, as well as along the south coast. Typical temperatures, 16-20°C across the U.K & Ireland with a moderate south westerly / westerly wind.
Tuesday will be probably the best day of the week with just some showers across north western coasts to trouble the weather picture. So dry for Ireland and the U.K, with pleasant spells of sunshine and temperatures peaking in the low twenties for the south of England. I said dry for Ireland but later in the afternoon, we will see the next rain front wetting the feet of the Irish Teddy bear across Kerry (you can get an Irishman / woman to explain that to you). This rain will quickly cross Ireland overnight and into the U.K as that close-by, low pressure system swirls in closely packed fronts of rain. That first front of rain will cross the western half of the U.K by the morning rush hour but as Ireland will find out, there's plenty more rain behind it. So another front is set to cross Ireland and the U.K later in the afternoon. As the low pressure moves east, it pulls down northerly winds, so during Wednesday, we see the wind change round from the west to the north. Cool and wet then.
Thursday sees a pause in the rainfall and a drier interlude. Not totally dry though and we will see showers across north western coasts and these will consolidate over Scotland and northern England later in the day. For most Thursday will be a sunshine and showers type of day with the main showers affecting the north / north east of Ireland and the U.K. Winds will be north westerly and temperatures, not too shabby with 20°C across the south of England.
We close the week on Friday with that rain still across central and eastern Scotland and The North East. During the day, two things happen to that rain, it consolidates and moves south into the east and south east of England. So wet down the eastern side of the U.K, but drier and nicer further west across Wales and Ireland. Later in the early evening, we see rain push into Kerry (again). North west winds will continue and these will hold temperatures down in the high teens.
How do we look for the weekend ?
Well we continue that unsettled theme with rain across Ireland, Scotland, the north west of England, Wales and The South West / south coast as well as East Anglia. Later in the day, that rain moves inland and threatens a wet ride back from MotoGP, Silverstone for me :( Winds will be lighter and more westerly with temperatures in the 17-19°C sort of range. Ireland starts dry, except across Leinster but later more general rain will develop. Sunday is drier, except for East Anglia where the last trailing arm of that low pressure will bring more rain later in the day. Elsewhere drier but still some showers around I am afraid though Ireland looks cloudy but drier on Sunday.
Now then there is a potential change on the way next week with a ridge of an Atlantic high pressure nudging up behind an uplift in the position of the jet stream.
Does this mean a change to drier and warmer conditions ?
Well possibly.....Above is the GFS prediction for next Wednesday and you can clearly see the heat plume characteristic as a high pressure system forms under a peak pattern in the jet stream. Looking at this I'd say we are on for a warmer, settled spell of weather with temperatures climbing into the mid-twenties, maybe higher. Now before you all get excited, currently it doesn't look like it'll last as we have a sneaky southern-biased low pressure system that may follow this peak w/c 14th August, but I am getting ahead of myself.
So I think next week will pan out like this ;
Starting unsettled on Monday with that low pressure still bringing rain to Scotland and The North East. Some of this rain will extend further south across East Anglia. As the high pressure builds early next week, it'll vector the rain north east across the north of Ireland and Scotland leaving areas south of this dry and increasingly warmer. As we approach mid-week, next week, the picture becomes more settled including across Scotland and the north, so warm, dry and settled for the 2nd part of next week. So a much better forecast than we have had of late with more than a hint of summer 😎
One topic to chat about today and that is disease pressure.
Over the last two weeks we have picked up a combination of conditions, particularly overnight ;
High overnight temperatures
Extended periods of plant leaf wetness
You don't need to be a practising plant pathologist to know that this combination of climatic conditions, more typical of autumn, are likely to initiate foliar pathogen activity.
So it's no surprise to see social media populating with images of Microdochium, Dollar Spot, Red Thread and the like. I also expect to see an uplift in Take All activity after the run of cooler, wetter weather we have endured through July.
I picked some data from a Davis weather station located in Sevenoaks, Kent and ran some stats looking at likely Microdochium nivale pressure over the last two weeks.
It shows clearly we experienced three distinct peaks, increasing in magnitude.
The two peaks on 22/23rd July and 27th/28th July were caused by long periods of plant leaf wetness as well as other factors. So if you are looking at some disease activity whether it be Microdochium or Dollar Spot, then that is your reason. Now normally I wouldn't expect to see aggressive Dollar Spot till we get to the end of August / early September when night length extends significantly and therefore the period of potential dew formation does likewise. The reason we are seeing it now is because we have experienced a false autumn spell of weather and that has really kicked in pathogen activity.
Looking ahead this week, I expect that to drop significantly as we pick up those cooler northerly winds but as we see potentially warmer weather next week, depending on the climatic characteristic of that warmer weather (humidity associated with it), we could see a resurgence of activity for a time.
Dropping the stats into the Smith Kerns model for the same location shows how disease pressure has been present through the month with significant periods > 20%.
So a testing month for quite different reasons to the previous one. I wonder what I'll be writing at the end of August ?
All the best.